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I'l like the ability to never HAVE to eat again, but I wouldn't want to lose the ability to eat at all. Eating is enjoyable. One would hope that you could control the photosynthesis to keep from getting too fat, though.

Slugs aren't very energetic. It's doubtful that photosynthesis alone will provide the energy necessary to power your body and that meat based computer in your head. You would still need to ingest a fair amount of food, in order to extract the concentrated energy contained in it.

I just did a few quick calculations. Assuming humans have 2 square meters of skin, and stood naked in direct sunlight in the best conditions for 8 hours per day, and assuming 5% efficiency for photosynthesis, we would only get enough energy to provide for 11 hours of sleep (250 BTU/hr), 7 hours of sitting still (400 BTU), 4 hours of light work (650 BTU) or 1 hour of heavy work (2400 BTU). We'd still probably need to consume 2/3 or so of our normal caloric intake from food.

Especially in Third world countries where there is plenty of sun, not much food and not much to do other than subsistence living,. At least it would be enough to get a lot of starving humans through the dry famine months that they get in thrid world countries near the equator.

Interestingly, this estimate is right around the theoretical maximal efficiency of photosynthesis. As outlined in Current Opinion in Biotechnology2008, vol. 19, pp. 153-159 (sorry, subscription only), the maximum theoretical efficiency of C3 photosynthesis is a mere 4.6%. C4 photosynthesis has a bit higher potential at 6.0%.

We can't even reach these efficiencies in plants (best for crops in a growing season is 2.4% for C3 or 3.7% for C4; see above reference), so sarahbau is right in saying that the amount

Yeah. I know it's not perfect, and that all 2 m^2 of skin wouldn't actually be receiving full sunlight. I was just trying to emphasize that even with unrealistically optimal conditions, we wouldn't get nearly enough energy from the sun to live on photosynthesis alone.

Yeah. I know it's not perfect, and that all 2 m^2 of skin wouldn't actually be receiving full sunlight. I was just trying to emphasize that even with unrealistically optimal conditions, we wouldn't get nearly enough energy from the sun to live on photosynthesis alone.

we just need to evolve (or bioengineer) larger backs to catch more sun. Note that the creature doing photosynthesis has quite a large back

Perhaps the GP planned to unzip his skin down the back, peel it forward, and present his entire "surface area" to the sun? ** shudder **

There are lots of options; the human body is flexible. Remember that Goatse guy?
I bet there are other areas of the human body which can be slowly trained and stretched over time,
until finally you are able to zip down your pants and fold out your bright green, photosyntesizing scrotum.

The point I think you (and GP, and the submitter, and many others) are missing is, photosynthesis does not remove the need to eat. Energy isn't the only thing you get from food. If you had vitamin pills so effective that you could live on them, plus sugar, plus water - and nothing else - then you could replace the sugar with the ability to perform photosynthesis. Such pills do not exist.

If you can make that light coherent and focused, you can be some sort of super hero. Laser Pointer Assisted Presentation Man! Is it a CEO? Is it a college professor? No! It's Laser Pointer Man! Boring wrongdoers into soporific oblivion at the speed of light! Taunting cats in his free time...

Modern man in effect eats a fair bit of oil and coal. It allows them to generate light, travel great distances fast etc.My car consumes about as much in $$$ terms as I do per month.

But yeah, being a superhuman could be fun:).

What you might want in addition to your lightbeams and electric zapping superpowers is the ability to use energy from an external power source to power your anaerobic metabolic modes = e.g. you can sprint and not get tired[1] till you run out of energy from that power source.

Well, the problem would be that you then would also be very hot. And not in the good sense. More in the “spontaneous combustion” sense.;)

But I agree that a way to not use unnecessary calories without an effort would be great. Decadent beyond belief. But great.;)

You already have metabolized it into a storage. That’s your fat. You just never use it up. I once calculated, that if released all at once, the fat in my body would give enough power to run a flux compensator for 0.88 seconds. No

If you would be so kind as to go soak your head in a large reservoir of liquid nitrogen for a few hours, you'll have your opportunity. Your head will be radiating light/heat at a blackbody temperature around 77K, which is (a) invisible and (b) cold. For the "dry water" part, well, frozen tissue at 77K really isn't very "wet" at all, except in the chemical sense.

In a normal plant cell is the chlorophyll produces by the cell and then shuttled to the chloroplast to be used or does the chloroplast itself produce the pigment within it's own membrane? If the latter, I would imagine this gene in the slug is redundant as the creature has to eat algae for the chloroplasts anyways.

Chloroplasts, just as with mitochondria, have a small DNA genome of their own. Due to the endosymbiotic relationship that has formed between chloroplasts and their photosynthetic hosts, chloroplasts have found it convenient to offload the majority of their genes to the nucleus. It is estimated that about 90% of the genes necessary for photosynthesis are nuclear, with the rest in chloroplasts, so these sea slugs appear to have acquired the nuclear genes, but not the chloroplast genes.

Chlorophyll itself is made in the cytoplasm, and actually requires relatively few new genes for an animal to be able to produce it, since the complicated steps of its biosynthesis are identical to the heme structures it is already able to make. The real difficulty, and one that this sea slug seems to have been able to surmount according to the Wikipedia page, is the production of the "oxygen-evolving complex," a metalloenzyme with a manganese-calcium core which transfers absorbed energy to a bound water molecule to break it into electrons, protons, and molecular oxygen. Heterotrophic organisms don't produce anything like it.

The article seems to indicate that the genes to produce chlorophyll can be passed on to offspring. But then:

The slugs accomplishment is quite a feat, and scientists aren't yet sure how the animals actually appropriate the genes they need.

Wouldn't that be a fluke that only needed to happen once?
They do point out that the animals also have to get chloroplasts by eating plant material (these are not passed on to offspring), so perhaps they meant to say they aren't sure
how they appropriate the chloroplasts. I would agree that's a really good question.

Some species of Sea Slugs have another similar interesting ability -- to adsorb and host nematocysts (stinging cells) from jellyfish and hydrozoans they've eaten, and use them for their own defense. The mechanism is substantially different (foreign cells are sequestered in specialized sacs, compared to the intracellular hosting of an organelle) though.

Couldn't you just form an symbiotic relationship with algae or photoplankton, allowing them to live inside you for protection in return for using them for energy? Aren't there already animals that do this?

Couldn't you just form an symbiotic relationship with algae or photoplankton, allowing them to live inside you for protection in return for using them for energy? Aren't there already animals that do this?

There are. That process is well understood, and thus, not all that interesting to scientists. What this slug does in addition to that is novel and thus interesting.

Building and repairing too. And well, there are those that enjoy the taste of some food. Anyway, having an extra source of energy won't hurt, you dont always need to be building and repairing, or at least could do it in a less urgent way than for getting the energy needed to live.

No. Studying something unique in the animal kingdom for 20 years does not make it evidence for anything. The slug is able to build chlorophyl from borrowed chloroplasts -- something no other animal has done. How long it's been doing that, we don't know. It's something cool and something that biological researchers can observe and attempt to understand outside of the pseudoscientific holy war of the church of evolutionism vs. all other religions. Dragging evolutionism vs creationism into this will only

Eating the brains of our slain foes is probably as close as we'll ever get to a Highlander quickening. These slugs are already workin' their way up the ladder, and they just might be coming for YOUR brains in a few years....

No I didn't read the article, MSNBC rarely loads properly here at work.
I believe that saying it gains energy via photosynthesis is incorrect. Photosynthesis causes a chemical reaction that converts Carbon Dioxide and Water (CO2 and H2O) into Sugar and Oxygen (C6H12O6 and O2). The sugar is then metabolized (correct term?) into energy.

Converting CO2 and H2O to sugar and oxygen requires energy, that energy comes from the sun. So saying that it obtains energy via (which means "by way of") photosynthesis is correct.

No, the statement is essentially correct. The slugs harvest (i.e. gain) energy via trapping photons with chlorophyll. They store that energy as chemical bonds in sugar molecules. They then release the energy as needed by metabolizing the sugar. Photosynthesis is the coupled capturing and storing of energy so saying that it "gains" energy via photosynthesis is a reasonable simplification.

Slugs have somehow included algae DNA with its own, and are now capable of actual photosynthesis. The DNA that was copied didn't code for the creation of chloroplasts, so the slugs have to consume a sufficient amount of algae before they can begin the process.

As long as they are exposed to light for 12 hours per day, they can live without the need for food.

Here's the thing. Animal cells have the ability to do a lot of biochemistry, but they have very limited ability to do some exotic chemistry that is essential to animal life. The major example of this is a molecule called adenosine triphosphate, aka ATP. All life uses ATP as an energy source.... lemme back up. Chemical reactions are reversible. To get from the reactants to the products requires that you put in a certain amount of energy to

Well to properly nitpick - to take out the energy middleman you'd need to firstly be your own fusion device as the sun is the real middleman. The sun isn't the source of energy it is simply an energy source as atoms are a source of energy, the sun just brings them together.